On 4/8/2013 9:08 AM, Francis C. wrote:
sms wrote:

USB ports were not designed to be used as chargers, but the USB 3.0 spec
has addressed the charging issue pretty well.

I'm a little confused ...

I have both USB 3.0 and USB 2.0 ports on my Linux laptop.

Should I expect them to work differently with a standard USB-to-mini
cable with the Motorola RAZR V3?

Yes, no, maybe so.

There's no short answer. A USB 3.0 port _could_ provide a higher maximum
current if the computer manufacturer decides to provide the higher
current, but it's not required.

A USB 2.0 port should supply a mininum of 500mA and is technically
required to shut down if the current exceeds 1.25A. A USB 3.0 port
should supply a minimum of 900mA and is supposed to shut down at 1.5A.
But there are also higher power options if communications is not
occurring simultaneously.

The reality is that both the USB 2.0 and 3.0 ports probably are able to
provide 900mA, but this depends on the laptop. For example, I have a
Dell netbook that shuts the USB ports down at about 700mA, but on other
machines I have they'll go well over 1000mA.

I doubt if the USB driver and the phone are smart enough to negotiate to
provide 900mA if the cable is plugged into the higher power port.
Remember, it's the phone that decides how much current to try to draw
from the USB port. The phone manufacturer has to err on the side of
caution and draw only 500mA from the USB 2.0 port even though most USB
2.0 ports could supply more than 500mA.